Latam Investor article17 Mar 2021 17:16
https://latam-investor.com/wp-content/uploads/2021/03/LatAm-INVESTOR-Spring-2021.pdf
Page 28, article about Cascabel.
In January the firm postponed the publication of a Pre-Feasibility Study (PFS) that had already been delayed. The share price understandably fell on the news but interim CEO, Keith Marshall, who was originally brought in to SolGold in November to analyse the PFS, says that investors need to be patient. “It’s very important to get the PFS right because once you move onto the Definitive Study it is very difficult to make any changes as you have lots of work streams going on in parallel.”
The old plan for the PFS was “high risk”, explains Marshall. “It was high risk in terms of execution because it was aiming to build the world’s largest underground mine in a record time and that rang alarm bells in my mind. The plan for a mine like this needs to be robust, so we can build it on-time and on-budget. Yet with the proposed PFS, I didn’t feel that was the case.”
The fact that Alpala’s ore body is deep underground, coupled with its environmentally sensitive location in a virgin mining jurisdiction, means that Cascabel needs to be a subterranean mine. Traditionally subterranean mines are far more expensive than open cast operations. The only way to make them competitive is to mine with block caving.
“Block caving is a particularly challenging mining method”, explains Marshall, “because it involves multiple different parameters. The basic concept is that you have a lattice of tunnels below the deposit, allowing access for loaders (boggers) that can move the ore to ore passes. Then you undercut the ore body by mining the undercut level. You basically mine a
great big slice of rock out from below the ore body and the orebody then starts to stress like the key stone in a bridge arch. Eventually the ore body is crushed, breaks and falls, and as you remove that material, the rock above breaks and falls and eventually you get a continuous supply of broken ore in the drawpoint. It sounds simple but as the rock mass breaks the stresses and tensions get redistributed around the cave and put stress on all the tunnels. There are mines that have lost
whole sections of the cave so it’s really important that the geotechs have the information they need."
It's certainly more complex than an open cast, or even a conventional underground mine, but there are significant benefits, says Marshall. “The big advantage of block caving is the operating cost. It’s the cheapest form of underground mining, with operating costs typically between $5 to $10 per tonne. In fact, it’s the only underground method that can compete with open pit mining on cost. But it brings a level of complexity that can’t be underestimated. I’ve developed a lot of block caving mines and there is normally a bit of pain at the beginning before you get it right. Once everything is working the cost advantage is phenomenal and it usually makes for a very profitable mine."
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